The invention relates to an impact crusher, especially for crushing stone, having a housing which comprises a delivery chute for supplying the material to be crushed to a rotor which is mounted in the housing, the rotor having beater blades, and rotating about a horizontal axis, the housing also comprising rebound walls, which approach the rotor in the region of the upper quadrant of the descending side of the rotor and form, with the latter, a delivery opening for the crushed material.
An impact crusher of this type is known (see Austrian Patent Specification Nos. 319019 and 332712), in which the rebound walls are formed by a rebound mechanism which is suspended about an axis, parallel to the rotor axis, so as to be pivoted away from the rotor. The rebound mechanism ends in the region of a delivery opening in a wall part which extends approximately tangentially to the circular path of the rotor. The pivotable arrangement of the rebound mechanism enables the width of the opening to be adjusted as required.
A similar embodiment is described in Austrian Patent Specification No. 288827 wherein the rebound plates forming the rebound walls are arranged on a plurality of rocker arms which are pivotable about an axis parallel to the rotor axis. The rocker arms, which are arranged parallel to one another and side by side, are supported on the crusher housing by springs, so that the rebound plates can also move to one side in order to adjust the width of the opening if foreign bodies or stones which are too large enter the delivery opening.
Austrian Patent Specification No. 289522 also describes an impact pulverizer in which the rebound walls are formed by rebound plates arranged next to and spaced from one another and extending in the axial direction of the rotor. The surfaces of these rebound plates, which extend transversely to the direction in which the stones are delivered, are inclined at different angles towards the vertical plane, the delivery opening being defined by a grinding plate, the surface of which extends approximately tangentially to the circular path of the rotor.
In the impact crushers of the described type the stones are crushed on one hand by the direct action of the beater blades of the rotor and on the other by the impact of the stones on the rebound walls. The extent to which the material is crushed is determined in particular by the width of the delivery opening. The large stones which are delivered may not always break immediately when coming into contact with the beater blades, as a result of which fairly large stones may settle at the entrance of the delivery opening and become wedged there between a beater blade and the rebound wall adjacent the delivery opening. As a result, the machine may be seriously damaged or ruined. Although considerable damage is prevented if the rebound walls are suspended so as to be pivotable, the stones pass through the machine without being crushed. However, in the case of fixed rebound walls, and if the pivotable rebound walls do not move to one side quickly enough, the rotor, the rotor shaft and the drive devices are usually damaged. In comparison to their size, only relatively small and easily breakable stones can therefore be treated by the known impact crushers. These machines also require a considerable amount of power for their drive.
The object of the present invention is to improve the hitherto known impact crushers so that even fairly large stones cannot become jammed in the region of the delivery opening.